A lot of people wrote T-Mobile off when its big merger with AT&T fell through last year. The pink carrier had no iPhone, no 4G. But with yesterday's announcement of the company's official LTE rollout, it may have just put itself in a position to offer something no one else can.

For the past few years T-Mobile has been focusing its efforts on its HSPA+ network, which has data speeds up to 42Mbps. Now, that isn't as high as LTE's theoretical maximum, but in practice we've found that HSPA+ speeds are almost as fast as LTE speed. When testing the Nexus 4 on T-Mo, for instance, we got download speeds of 16Mbps and 2Mbps uploads. Not bad at all.

Why does that matter? Because T-Mobile's isn't replacing its lightning quick HSPA+ network with LTE. It's just building it out in addition. That's going to make a huge difference.

Say you're on Verizon, enjoying your wicked fast 4G data thanks to its girthful LTE network. Hit a low or no-coverage spot, though, and you get bounced over to its 3G network. That is a major dropoff in speed—typically going from 20Mbps to 1 or 2Mbps. Suddenly, it'll be hard to stream music, and web browsing will crawl by comparison. Even AT&T's HSPA network (HSPA 21Mbps) is only about half the speed of T-Mobile's (HSPA 42Mbps). In other words, T-Mobile's backup is fast enough that you probably won't even notice that you're on the backup, which is pretty awesome. (For a look at how LTE works, check this out.) T-Mobile will offer guaranteed uninterrupted zip, something no other carrier can.

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We're not there yet, though, unfortunately; T-Mobile's LTE won't be live in until the end of March, it will take the company until the end of the year to cover 100 million people. (Update: That's actually 100 million by mid-year, and 200 million by year's end.) Your LTE choice is also limited; the only LTE device T-Mobile currently has is the Galaxy Note II, which will have LTE enabled through an OTA update coming this week. Hope is coming, though; the BlackBerry Z10 will launch with LTE, and we expect that the Galaxy S IV and the HTC One will as well.

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T-Mobile still has a lot to prove but if it can successfully deliver everything it's promising, it will be offering something the other networks can't. Whether that's enough enough to make you switch, of course, is another question entirely.